The present invention relates to a method of manufacturing a fiber-reinforced resin pipe, and, more particularly, to a method of manufacturing a tubular body by a resin injection process (RI process) used in effecting fiber-reinforced plastic molding.
Conventionally, manufacture of a tubular body by the RI process comprises the steps of: winding a sheet-like reinforcing fiber such as a mat or a roving cloth of a fiber glass or a carbon fiber on a core; placing the reinforced fiber wound on the core within an outer mold; and injecting and curing a resin in the outer mold.
Manufacture of a fiber-reinforced resin tubular body is also possible by using a dry-filament-winding process, and this method comprises the steps of: winding a continuous fiber on a core; placing the continuous fiber wound on the core within an outer mold; and injecting and curing a resin in the outer mold.
However, the former method has such disadvantages that a density of fiber contained in a molded product cannot be increased although a resin-impregnating ability becomes good because of a loose structure of the sheet-like fiber and that the provision of a molded product of an increased strength is impossible.
On the other hand, the latter method makes it possible to wind the fiber at a high density by the filament winding process, so that the density of the reinforcing fiber contained in a resultant product becomes high. However, the resin-impregnating ability of the fiber becomes remarkably degraded, with the result that some portions which are not impregnated with resin are apt to remain even when the pressure of the injection of the resin is increased. Reduction in the winding tension for the fiber is apt to cause a disarray of the fiber when the resin is injected under high pressure.
A wet winding process is also known in which a continuous fiber having been impregnated with a resin is wound on a core and is then cured so as to form a resin pipe. This process, however, suffers from the disadvantage that a molded product has a bad appearance due to the non-use of an outer mold.